Hard coating agent and film with hard coating

ABSTRACT

The present invention provides a hard coat agent which comprises (A) an ultraviolet curable substance having 5 to 7 function groups, (B) an urethane acrylate oligomer having 2 to 3 function groups and (C) an oligomer type ultraviolet polymerization initiator. The hard coat film can decrease the curl caused by the heat shrinkage and prevent cracking and peeling of the hard coat layer caused by bending, and therefore, is excellent in bending resistance. Also, the hard coat film is excellent in the adhesion property between the hard coat layer and the substrate, pencil hardness of the hard coat layer and abrasion resistance of the hard coat layer.

FIELD OF THE TECHNOLOGY

The present invention relates to a hard coat film which can be used as aprotective film for liquid crystal display devices, CRT(cathode-raytube) display devices, plasma display devices, electrochromic displaydevices, light emitting diode display devices, EL (electroluminescence)display devices et al. and parts of display devices such as touchpanels, and can be used as a functional film, and a hard coat agentwhich can be used in the hard coat film.

BACKGROUND TECHNOLOGY

In recent years, for protecting various displays et al., the displayshave been superimposed with a plastic film. Plastic films which containa hard coat layer obtained by coating with an active energy ray curableresin and are treated with surface-treatment such as low reflectiontreatment and antistatic treatment have been used as the protectingplastic films.

However, there were problems that curl of the protecting plastic filmswas caused by heat treatment in the surface-treatment, and crackings andpeelings of hard coat layer in the protecting plastic films were causedby bending at processing of the protecting plastic films.

An object of the present invention is to provide a hard coat film whichcan decrease the curl caused by the surface-treatment and is excellentin the adhesion property of the hard coat layer, hardness, bendingresistance and abrasion resistance, and a hard coat agent which can beused in the hard coat film.

DISCLOSURE OF THE INVENTION

Extensive investigations undertaken by the present inventors directed tothe object described above have led to the discovery that the object canbe achieved by forming a hard coat layer on the substrate, wherein thehard coat layer is formed by applying on the substrate with a curablecomposition containing a specific ultraviolet curable substance and anoligomer type ultraviolet polymerization initiator as a hard coat agentand then curing by ultraviolet ray irradiation to the applied curablecomposition to obtain the hard coat film.

The present invention thus provides a hard coat agent which comprises(A) an ultraviolet curable substance having 5 to 7 function groups, (B)an urethane acrylate oligomer having 2 to 3 function groups and (C) anoligomer type ultraviolet polymerization initiator.

In another aspect, the present invention provides the hard coat agent asdescribed above, wherein an content ratio of an urethane acrylateoligomer having 2 to 3 function groups of ingredient (B) is 5 to 30parts by weight against to 100 parts by weight of total amount ofingredient (A) and ingredient (B).

In another more aspect, the present invention provides the hard coatagent as described above, wherein the ultraviolet curable substancehaving 5 to 7 function groups of ingredient (A) is an ultravioletcurable urethane acrylate oligomer having 5 to 7 function groups or anultraviolet curable acrylate having 5 to 7 function groups.

In further aspect, the present invention provides a hard coat film whichcomprises a substrate and a hard coat layer, wherein the hard coat layeris formed by applying on the substrate with the hard coat agent asdescribed above and then curing by ultraviolet ray irradiation to theapplied hard coat agent layer.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a plane view and a side view of a fixture for measuringheat curl of a hard coat film.

In the drawing, 1 is a hard coat film, 2 is a circular frame and 3 is afastener.

PREFERABLE EMBODIMENT FOR PRACTICING THE INVENTION

The ultraviolet curable substance having 5 to 7 function groups, whichis used in the hard coat agent of the present invention, has a propertyof curing caused by irradiating ultraviolet ray and includes unsaturatedmonomers having 5 to 7 function groups, oligomers having 5 to 7 functiongroups, resins having 5 to 7 function groups, or compositions thereof.Examples of the ultraviolet curable substance having 5 to 7 functiongroups include ultraviolet curable substance having 5 to 7 functiongroups such as acrylates, urethane acryaltes and polyester acrylates.

The preferable ultraviolet curable acryaltes having 5 to 7 functiongroups include xylitol penta(meth)acrylate, dipentaerythritolpenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate and glyceryldipentaerythritol hepta(meth)acrylate.

The urethane acrylate is a compound having an urethane bond and an acrylgroup. The urethane bond is generated by addition reaction of a hydroxylgroup with an isocyanate group so that the urethane bond is introducedinto the urethane acrylate. The acrylate group is introduced into theurethane acrylate by addition reaction of the hydroxyacrylate.

Examples of the ultraviolet curable urethane acryaltes having 5 to 7function groups include urethaneacrylates obtained by reacting hydroxylgroups of polyol such as pentaol, hexaol and heptaol with a part ofisocyanate groups of polyisocyanate such as diisocyanates to produce anurethane compound having isocyanate groups, and then reacting theurethane compound having isocyanate groups with hydroxyacylate.

The ultraviolet curable substance having 5 to 7 function groups can beutilized by single member or a combination of two or more members.

The urethane acrylate oligomer having 2 to 3 function groups ofingredient (B), which is used in the hard coat agent of the presentinvention, has a property of curing caused by irradiating ultravioletray. The urethane acrylate has the structure described above. Examplesof the ultraviolet curable urethane acrylate oligomer having 2 to 3function groups include urethaneacrylate oligomers obtained by reactinghydroxyl groups of polyol such as diol and triol with a part ofisocyanate groups of polyisocyanate such as diisocyanates to produceurethane compound having isocyanate groups, and then reacting theurethane compound having isocyanate groups with hydroxyacylate.

The ultraviolet curable urethane acrylate oligomer having 2 to 3function groups can be utilized by single member or a combination of twoor more members.

The content ratio of the urethane acrylate oligomer having 2 to 3function groups is preferably 5 to 30 parts by weight, more preferably 7to 25 parts by weight against to 100 parts by weight of total amount ofingredient (A) and ingredient (B).

In the hard coat agent of the present invention, an oligomer typeultraviolet polymerization initiator is comprised.

The oligomer type ultraviolet polymerization initiator is an ultravioletpolymerization initiator having two or more repeat units havingultraviolet polymerization initiation activity and is preferably anultraviolet polymerization initiator having 2 to 50 of the repeat units.Examples of the oligomer type ultraviolet polymerization initiatorinclude an oligomer type ultraviolet polymerization initiatorrepresented by formula (1):

wherein Y is a linear or branched alkylene group, R¹ and R² are a linearor branched alkyl group and may form a ring by bonding each other, and nis an integer of 2 to 50.

The number of carbon atoms in a linear or branched alkylene group of Yis not limited particularly and preferably 1 to 10, more preferably 1 to6, most preferably 1 to 3. The number of carbon atoms in a linear orbranched alkyl group of R¹ and R² is not limited particularly andpreferably 1 to 8, more preferably 1 to 5, most preferably 1 to 3. Theinteger, n, is preferably 2 to 20, more preferably 2 to 10, mostpreferably 2 to 6.

The terminal of the chain of repeat unit in the oligomer typeultraviolet polymerization initiator are each bonded with a substitutiongroup. The substitution group may be a group derived from an oligomerpolymerization initiator or may be a group derived from an oligomerpolymerization terminator and includes usually hydrogen atom andhydrocarbon groups. The hydrocarbon groups include, for example, alkylgroup, cycloalkyl group and aryl group. Alkyl group includes lower alkylgroups such as methyl group, ethyl group, propyl group and butyl group.Cycloalkyl group includes cyclohexyl group, cycloheptyl group,cyclooctyl group and alkyl group-substituting group thereof. Aryl groupincludes phenyl group and alkyl group-substituting group thereof.

Examples of the oligomer type ultraviolet polymerization initiatorinclude poly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}propanone],poly[2-hydroxy-2-methyl-1-{4-vinyl-phenyl}propanone],poly[2-hydroxy-2-ethyl-1-{4-(1-methylvinyl)phenyl}propanone],poly[2-hydroxy-2-ethyl-l-{4-vinyl-phenyl}propanone],poly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}butanone],poly[2-hydroxy-2-methyl-1-{4-vinyl-phenyl}butanone],poly[2-hydroxy-2-ethyl-1-{4-(1-methylvinyl)phenyl}butanone] andpoly[2-hydroxy-2-ethyl-1-{4-vinyl-phenyl}butanone].

The oligomer type ultraviolet polymerization initiator can be utilizedby single member or a combination of two or more members.

The content ratio of the oligomer type ultraviolet polymerizationinitiator is usually preferably 0.01 to 20 parts by weight, mostpreferably 0.1 to 10 parts by weight against to 100 parts by weight oftotal amount of ingredient (A) and ingredient (B).

The hard coat agent of the present invention can be formulated with afiller such as silica, which includes colloid silica, silicone powder,mica, glass bees, acrylic fine powder and hollow particulate to addnonglaring property. The amount of the filler is preferably 0.5 to 50parts by weight against to 100 parts by weight of the hard coat agent.When the amount of the filler is less than 0.5 parts by weight, thenonglaring property decreases. When the amount of the filler is morethan 50 parts by weight, the strength of the film decreases.

The hard coat agent can contain an antimicrobial agent. Theantimicrobial agent includes various antimicrobial agents such as silverinorganic antimicrobial agents including silver inorganic antimicrobialagent having zirconium phosphate as a support, silver inorganicantimicrobial agent having zeolite as a support, silver inorganicantimicrobial agent having calcium phosphate as a support, silverinorganic antimicrobial agent having silica gel as a support; amino acidorganic antimicrobial agents including organic antimicrobial agentcompounded with an amino acid compound; organic antimicrobial agentscompounded with a nitrogen-containing sulfur compound.

The amount of the antimicrobial agent can be selected according to thekind of the antimicrobial agent, required antimicrobial property and theholding time et al.

The hard coat agent can contain additives such as a light stabilizer, anultraviolet absorbent, a catalyst, a coloring agent, an antistaticagent, a lubricant, a leveling agent, a defoaming agent, apolymerization promotor, an antioxidant, a flame retardant, an infraredabsorbent, a surface active agent and a surface modifier.

The hard coat agent can contain a diluent for easy application. Thediluent includes aromatic hydrocarbons such as benzene, toluene andxylene; aliphatic hydrocarbons such as hexane, heptane, octane, nonaneand decane; and ketones such as methyl ethyl ketone, diethyl ketone anddiisopropyl ketone. The amount of the diluent can be selected to be therequired viscosity.

The substrate film of the hard coat film of the present invention is notlimited particularly when the substrate film is transparent orsemitransparent, and includes, for example, films such as films ofpolyester resins, polyethylene resins, polypropylene resins, polystyreneresins, polycarbonate resins or films thereof compounded with fillersuch as loading material in the range that transparency orsemitransparency is not damaged. Polyester resins include preferablypolyethylene terephthalate resins and polybutylene terephthalate resins.

A thickness of the substrate film is preferably in a range of from 10 to350 micrometers, more preferably in a range of from 25 to 300micrometers, most preferably in a range of from 50 to 250 micrometers.

The surface of the substrate film can be treated for easy adhesion. Theeasy adhesion treatments are not limited particularly and include acorona discharge treatment and a formation of layer of low molecularweight resin polymer which is the same as the resin of the substratefilm. For example, when the substrate film is made of polyester resin,for example, polyethylene terephthalate resin, the low molecular weightresin polymer includes low molecular weight polyesters, for example,ethylene terephthalate oligomers.

The hard coat film of the present invention has the hard coat layer onthe surface of the substrate film. The hard coat layer can be formedonly one surface or both surfaces of the substrate film.

The hard coat layer can be formed by applying on the substrate with ahard coat agent containing an ultraviolet curable substance and thencuring by ultraviolet ray irradiation to the applied hard coat agent.

A thickness of the hard coat layer is not limited particularly andusually preferably in a range of from 1 to 50 micrometers, morepreferably in a range of from 2 to 30 micrometers, most preferably in arange of from 3 to 20 micrometers.

In the hard coat film of the present invention, the hard coat agent ofthe present invention is applied on the substrate and cured byultraviolet ray irradiation to form the hard coat layer.

Methods of applying the hard coat agent to the substrate film include,for example, conventional known methods such as bar coater method, knifecoater method, roll coater method, brad coater method, die coatermethod, gravure coater method and curtain coater method.

As the irradiated ultraviolet ray, ultraviolet ray radiated from anultraviolet lamp can be usually used. As the ultraviolet lamp, theultraviolet lamp such as high-pressure mercury lamp, fusion H lamp andxenon lamp, which emit an ultraviolet ray having a spectrum distributionin the area of 300 to 400 nm of wave length, can be usually used. Theirradiation amount is usually in the range of 100 to 500 mJ/m².

The irradiation of ultraviolet ray is preferably carried out under theatmosphere containing no oxygen or low level concentration of oxygen.The oxygen concentration in the low level concentration of oxygen ispreferably not more than 5 percents, more preferably not more than 3percents, and most preferably not more than 2 percents. Gas other thanoxygen in the atmosphere containing no oxygen or low level concentrationof oxygen, is preferably inactive gas. The inactive gas includesnitrogen, helium, neon and argon.

The hard coat film of the present invention can be used as a protectivefilm for liquid crystal devices, CRT(cathode-ray tube) display devices,plasma display devices, electrochromic display devices, light emittingdiode devices, EL (electroluminescence) display devices et al. and partsof display devices such as touch panels, and can be used as a functionalfilm.

For fitting the hard coat film of the present invention to an adherend,a pressure-sensitive adhesive layer can be formed on an opposite surfaceto the surface of the hard coat layer in the hard coat film.

As a pressure-sensitive adhesive used in the pressure-sensitive adhesivelayer, various pressure-sensitive adhesives can be used. The variouspressure-sensitive adhesives include, for example, acrylicpressure-sensitive adhesives, silicone pressure-sensitive adhesives,rubber pressure-sensitive adhesives and polyester pressure-sensitiveadhesives.

The pressure-sensitive adhesive can contain a tackifier, a filler, asoftener, an antioxidant, an ultraviolet absorbent and a curing agentaccording to needs. The tackifier includes rosin resins, terpene phenolresins, terpene resins, aromatic hydrocarbon modified terpene resins,petroleum resin, coumarone-indene resins, styrene resins, phenol resinsand xylene resins. The filler includes zinc white, titanium oxide,silica, calcium carbonate and barium sulfate. The softener includesprocess oils, liquid rubbers and plasticizers. The antioxidant includesanilide antioxidants, phenol antioxidants, phosphite antioxidants andthioester antioxidants. The ultraviolet absorbent includes benzophenoneultraviolet abosorbents and benzotriazole ultraviolets. The curableagent includes epoxy curable agents, isocyanate curable agents andmetallic chelate agents.

The thickness of the pressure-sensitive adhesive layer is usually in therange from 5 to 100 μm, and preferably 10 to 50 μm. For protecting thesurface of the pressure-sensitive layer, a release liner is preferablylaminated on the surface of the pressure-sensitive layer.

In the hard coat film of the present invention, the substrate film maybe printed and then the hard coat layer and the pressure-sensitiveadhesive layer may be formed, or the pressure-sensitive adhesive layermay be printed according to needs.

EXAMPLES

The present invention is described more specifically by reference toembodiments thereof. It should be noted that the present invention isnot intended to be limited by these embodiments.

An evaluation method of adhesion property, a measurement method ofpencil hardness, a bending resistance test, an abrasion resistance testand a measurement method of heat curl of the hard coat films obtained inexamples and comparative examples are described in the following.

(Evaluation Method of Adhesion Property)

A surface of the hard coat layer of the hard coat film was cut by acutter to form 100 cross hatchings wherein the size of one crosshatching is 1 mm×1 mm and then a cellophane pressure-sensitive adhesivetape (produced by NICHIBAN Co., Ltd.) was adhered on the surface of thehard coat layer. Next, the cellophane pressure-sensitive adhesive tapewas peeled from the surface. The adhesion property was evaluated bycounting the number of cross hatchings of the hard coat layer left onthe substrate. The evaluation of initial adhesion property was conductedby using the hard coat film which was left at room temperature for oneday.

(Measurement Method of Pencil Hardness)

The pencil hardness of the surface of the hard coat layer in the hardcoat film was measured by using a pencil scratching test machineaccording to JIS (JAPANESE INDUSTRIAL STANDARD) K5400.

(Bending Resistance Test)

According to JIS K5400, the hard coat film cut in 150 mm×50 mm wasbended at angle of about 180° around a shaft having specific diameter,as the surface of the hard coat layer was arranged outside. Next, thehard coat film was returned into the original position. Cracking andpeeling of the hard coat layer were observed by visual. Minimum diameterthat the cracking and peeling were not caused, was represented asbending resistance (unit: mm).

(Abrasion Resistance Test)

The surface of the hard coat layer was rubbed with Steel wool #0000.Condition of flaw was observed by visual and evaluated according to thefollowing ranking.

-   ◯: flaw was not observed.-   ×: flaw was observed.    (Measurement Method of Heat Curl)

A hard coat film cut in A4 size was fixed to the fixture as shown inFIG. 1 and placed into an oven to heat for 1 minute at 190° C. Next, thehard coat film was cooled to room temperature and then thesurface-treated hard coat film was cut in 100 mm×100 mm. The cut hardcoat film was placed into an oven under free condition without fixing tothe fixture and heated again for 30 minutes at 150° C. And then, the cuthard coat film was left at room temperature. The sample piece was placedon a horizontal bedplate. Each heights of 4 risen sides were measured.Average value of the heights was decided as the measurement value (unit:mm).

Example 1

Ten parts by weight of urethane acrylate oligomer having two functiongroups (produced by NIPPON SYNTHETIC CHEMICAL Co., Ltd., trade name“UV-3200”) and 5 parts by weight ofpoly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}propanone] (producedby LANBELTY CORPORATION, “ESACURE KIP150”, concentration: 100 percentsby weight) were added to 90 parts by weight of urethane acrylateoligomer having six function groups (produced by ARAKAWA CHEMICAL Co.,Ltd., trade name “BEAMSET 577”, concentration: 100 percents by weight)and mixed. Further, toluene was added to prepare a hard coat agenthaving 50 percents by weight of resin solid content. Thus, a hard coatagent was prepared.

Next, the hard coat agent was applied by a wire bar on one surface of apolyethylene terephthalate film of a thickness of 188 μm (produced byTOYO BOSEKI Co., Ltd., trade name “A4300”), in which both surfaces weretreated to improve adhesion property. And toluene was vaporized to formthe hard coat agent layer. And then, ultraviolet ray of high pressuremercury ultraviolet lamp (120 w/cm) was irradiated to the hard coatagent layer from the side of the layer under atmosphere of nitrogencontaining about 1 percent of oxygen concentration in the condition oftotal light volume of about 250 mJ/m². The hard coat agent layer wascured to obtain a hard coat film having a thickness of 5 μm. Theadhesion property, the pencil hardness, bending resistance, abrasionresistance and heat curl of the obtained hard coat layer were shown inTable 1.

Example 2

Twenty parts by weight of urethane acrylate oligomer having two functiongroups (produced by ARAKAWA CHEMICAL Co., Ltd., trade name “BEAMSET505B”, concentration: 100 percents by weight) and 5 parts by weight ofpoly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}propanone] (producedby LANBELTY CORPORATION, “ESACURE KIP150”, concentration: 100 percentsby weight) were added to 80 parts by weight of dipentaerythritolhexaacrylate (produced by NIPPON KAYAKU Co., Ltd., “KAYARAD DPHA”,concentration: 100 percents by weight) and mixed. Further, toluene wasadded to prepare a curable composition having 50 percents by weight ofresin solid content. Thus, a hard coat agent was prepared.

Next, the hard coat agent was applied by a wire bar on one surface of apolyethylene terephthalate film of a thickness of 188 μm (produced byTOYO BOSEKI Co., Ltd., trade name “A4300”), in which both surfaces weretreated to improve adhesion property. And toluene was vaporized to formthe hard coat agent layer. And then, ultraviolet ray of high pressuremercury ultraviolet lamp (120 w/cm) was irradiated to the hard coatagent layer from the side of the layer under atmosphere of nitrogencontaining about 1 percent of oxygen concentration in the condition oftotal light volume of about 250 mJ/m . The hard coat agent layer wascured to obtain a hard coat film having a thickness of 5 μm. Theadhesion property, the pencil hardness, bending resistance, abrasionresistance and heat curl of the obtained hard coat layer were shown inTable 1.

Comparative Example 1

Five parts by weight ofpoly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}propanone] (producedby LANBELTY CORPORATION, “ESACURE KIP150” concentration: 100 percents byweight) were added to 100 parts by weight of urethane acrylate oligomerhaving six function groups (produced by ARAKAWA CHEMICAL Co., Ltd.,trade name “BEAMSET 577”, concentration: 100 percents by weight) andmixed. Further, toluene was added to prepare a hard coat agent having 50percents by weight of resin solid content. Thus, a hard coat agent wasprepared.

Next, the hard coat agent was applied by a wire bar on one surface of apolyethylene terephthalate film of a thickness of 188 μm (produced byTOYO BOSEKI Co., Ltd., trade name “A4300”), in which both surfaces weretreated to improve adhesion property. And toluene was vaporized to formthe hard coat agent layer. And then, ultraviolet ray of high pressuremercury ultraviolet lamp (120 w/cm) was irradiated to the hard coatagent layer from the side of the layer under atmosphere of nitrogencontaining about 1 percent of oxygen concentration in the condition oftotal light volume of about 250 mJ/m². The hard coat agent layer wascured to obtain a hard coat film having a thickness of 5 μm. Theadhesion property, the pencil hardness, bending resistance, abrasionresistance and heat curl of the obtained hard coat layer were shown inTable 1.

Comparative Example 2

Ten parts by weight of urethane acrylate oligomer having two functiongroups (produced by NIPPON SYNTHETIC CHEMICAL Co., Ltd., trade name“UV-3200”) and 5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone(produced by CHIBA GIGY CORPORATION, “IRGACURE 184”) were added to 90parts by weight of urethane acrylate oligomer having six function groups(produced by ARAKAWA CHEMICAL Co., Ltd., tradename “BEAMSET577”,concentration: 100 percents by weight) and mixed. Further, toluene wasadded to prepare a hard coat agent having 50 percents by weight of resinsolid content. Thus, a hard coat agent was prepared.

Next, the hard coat agent was applied by a wire bar on one surface of apolyethylene terephthalate film of a thickness of 188 μm (produced byTOYO BOSEKI Co., Ltd., trade name “A4300”), in which both surfaces weretreated to improve adhesion property. And toluene was vaporized to formthe hard coat agent layer. And then, ultraviolet ray of high pressuremercury ultraviolet lamp (120 w/cm) was irradiated to the hard coatagent layer from the side of the layer under atmosphere of nitrogencontaining about 1 percent of oxygen concentration in the condition oftotal light volume of about 250 mJ/m². The hard coat agent layer wascured to obtain a hard coat film having a thickness of 5 μm. Theadhesion property, the pencil hardness, bending resistance, abrasionresistance and heat curl of the obtained hard coat layer were shown inTable 1.

Comparative Example 3

Five parts by weight ofpoly[2-hydroxy-2-methyl-1-{4-(1-methylvinyl)phenyl}propanone] (producedby LANBELTY CORPORATION, “ESACURE KIP150”, concentration: 100 percentsby weight) were added to 100 parts by weight of dipentaerythritolhexaacrylate (produced by NIPPON KAYAKU Co., Ltd., “KAYARAD DPHA”,concentration: 100 percents by weight) and mixed. Further, toluene wasadded to prepare a curable composition having 50 percents by weight ofresin solid content. Thus, a hard coat agent was prepared.

Next, the curable composition was applied by a wire bar on one surfaceof a polyethylene terephthalate film of a thickness of 188 μm (producedby TOYO BOSEKI Co., Ltd., tradename “A4300”), in which both surfaceswere treated with low molecular weight polyester resin to improveadhesion property. And toluene was vaporized to form the curablecomposition layer having a thickness of 3 μm. And then, ultraviolet rayof high pressure mercury ultraviolet lamp (120 w/cm) was irradiated tothe curable composition layer from the side of the layer in thecondition of total light volume of about 250 mJ/m². The curablecomposition layer was cured to obtain a hard coat film. The adhesionproperty and the gas generation in heat treatment of the hard coat filmand the pencil hardness of the hard coat layer were shown in Table 1.TABLE 1 Adhesion Pencil Bending Abrasion Heat property hardnessresistance resistance curl Example 1 100/100 2H 10 ◯ 8 Example 2 100/1002H 10 ◯ 10 Comparative 100/100 2H 18 ◯ 25 Example 1 Comparative 100/1002H 14 ◯ 9 Example 2 Comparative 100/100 2H 19 ◯ 29 Example 3

The hard coat film of the present invention can decrease the curl causedby the heat shrinkage and prevent cracking and peeling of the hard coatlayer caused by bending, and therefore, is excellent in bendingresistance. Also, the hard coat film is excellent in the adhesionproperty between the hard coat layer and the substrate, pencil hardnessof the hard coat layer and abrasion resistance of the hard coat layer.

1. A hard coat agent which comprises (A) an ultraviolet curablesubstance having 5 to 7 function groups, (B) an urethane acrylateoligomer having 2 to 3 function groups and (C) an oligomer typeultraviolet polymerization initiator.
 2. The hard coat agent as claimedin claim 1, wherein a content ratio of an rethane acrylate oligomerhaving 2 to 3 function groups of ingredient (B) is 5 to 30 parts byweight against to 10 parts by weight of total amount of ingredient (A)and ingredient (B).
 3. The hard coat agent as claimed in claim 1,wherein the ultraviolet curable substance having 5 to 7 function groupsof ingredient (A) is an ultraviolet curable urethane acrylate oligomerhaving 5 to 7 function groups or an ultraviolet curable acrylate having5 to 7 function groups.
 4. A hard coat film which comprises a substrateand a hard coat layer, wherein the hard coat layer is formed by applyingon the substrate with the hard coat agent as claimed in anyone of claims1 to 3 and then curing by ultraviolet ray irradiation to the appliedhard coat agent layer.